I. Field of the Invention
This invention relates to an optical switch.
More particularly, this invention is concerned with an optical switch which is mainly used as a shutter for intercepting or passing light signals and is characterized by having a small size and a light weight, and comprises a shutter operated by a piezoelectric actuator and a mirror for changing transmission directions of light signals.
II. Description of the Prior Art
Shutters for intercepting or passing light signals are typically classified into two types, i. e., mechanical shutters and non-mechanical shutters.
The mechanical shutters are operated by mechanical methods, such as rotating mirrors, lenses or prisms in the shutters or changing the connection point between fiber optic cables therein.
The non-mechanical shutters are operated by non-mechanical methods, such as by utilizing an acousticoptical effect or an electrooptical effect.
The heretofore known mechanical shutters are not suitable as they are quite cumbersome in that they are heavy and they require a large quantity of electric power, because motors are used in their driving systems to rotate or move the optical elements thereof. For example, a motor is used for rotating a polygon mirror which mirror is used to intercept the light signals, and further, preventative measures must be taken to take into consideration vibratory and electromagnetic noises of the motors.
On the other hand, the aforementioned non-mechanical shutters also have problems. The non-mechanical shutters which are operated by utilizing an electrooptical effect of PLZT (lanthanum doped lead zirconate-lead titanate), etc. are unsuitable or defective for our purposes in that the intensity of output light signals passed through the shutters is very much lower than that of input light signals to the shutters because polarizers and optical detectors used in the shutters absorb the input light signals.
Shutters which are operated by utilizing liquid crystals are also unsuitable or defective for our purposes in that S/N (signal to noise) ratios thereof become lower because the liquid crystals absorb incident light signals, and further the liquid crystals may be damaged by intensive light signals.
Shutters operated by utilizing CCD (charge-coupled device or electrocharge combination device) are also defective or unsuitable for our purposes in that light signals can not directly pass through the shutters because the light signals are converted to electric signals in the shutters.